The present invention relates to a porous shaped article of cellulose hydrate with an improved cleaning effect, especially a sponge cloth, and to a process for its manufacture.
Processes for preparing porous shaped articles of cellulose hydrate are known in the art. For this purpose, cellulose is first converted into viscose. In order to cause the formation of pores, a pore forming agent, such as salt grains, e.g. crystals of Glauber's salt of appropriate grain size are usually incorporated into the viscose, and, if desired, reinforcing fibers, e.g. cotton fibers of 12 to 15 mm length, may be incorporated as well. Then the mass is coagulated in a coagulating bath under the influence of heat, e.g. is precipitated in a water bath at approximately 100.degree. C. In case of preparing a flat shaped porous article, a layer of the mass advantageously is applied to an endless belt, by means of which it is introduced into the coagulating bath. In the water bath, a major portion of pore forming agent is eliminated, e.g. the salt is dissolved and washed away. The porous shaped article then passes through a regenerating bath containing aqueous sulfuric acid and, if appropriate, a chlorite bleaching bath. Next follows a washing step where the porous shaped article is throughly washed with water. Then it is dried. After drying, it may be cut to the desired size. Colored shaped articles are produced by adding dyes and color brighteners, which are mixed with the viscose.
Further, it has already been suggested to supply the heat required for quick coagulation by high frequency radiation or by infra-red radiation, or to use a crystalline salt containing water of crystallization, e.g. trisodium phosphate, in place of Glauber's salt. However, these suggestions did not find acceptance in the praxis of manufacturing sponges and sponge cloths.